FormatStringConcatenation

WARNING

Simplification

Summary

Defer string concatenation to the invoked method

Suppression

Suppress false positives by adding the suppression annotation @SuppressWarnings("FormatStringConcatenation") to the enclosing element.

Disable this pattern completely by adding -Xep:FormatStringConcatenation:OFF as compiler argument. Learn more.

Samples

Replacement

Shows the difference in example code before and after the bug pattern is applied.

 import static com.google.common.base.Preconditions.checkArgument;
 import static org.assertj.core.api.Assertions.assertThat;
 
 import java.util.Locale;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.slf4j.Marker;
 
 class A {
   private static final Logger LOG = LoggerFactory.getLogger(A.class);
 
   void assertj() {
-    assertThat(0).overridingErrorMessage(toString() + " str");
-    assertThat(0).overridingErrorMessage("str " + toString());
-    assertThat(0).overridingErrorMessage(toString() + toString());
-    assertThat(0).overridingErrorMessage("str " + toString() + " word " + new A().hashCode());
-    assertThat(0).overridingErrorMessage("str " + (toString() + " word ") + (hashCode() / 2));
+    assertThat(0).overridingErrorMessage("%s str", toString());
+    assertThat(0).overridingErrorMessage("str %s", toString());
+    assertThat(0).overridingErrorMessage("%s%s", toString(), toString());
+    assertThat(0).overridingErrorMessage("str %s word %s", toString(), new A().hashCode());
+    assertThat(0).overridingErrorMessage("str %s word %s", toString(), hashCode() / 2);
 
     // Flagged but not auto-fixed.
     assertThat(0).overridingErrorMessage("%s " + toString(), "arg");
   }
 
   void guava() {
-    checkArgument(true, "str " + toString());
+    checkArgument(true, "str %s", toString());
 
     // Flagged but not auto-fixed.
     checkArgument(true, "%s " + toString(), "arg");
   }
 
   void jdk() {
-    String.format("str " + toString());
-    String.format(Locale.ROOT, "str " + toString());
+    String.format("str %s", toString());
+    String.format(Locale.ROOT, "str %s", toString());
 
     // Flagged but not auto-fixed.
     String.format("{} " + toString(), "arg");
     String.format(Locale.ROOT, "{} " + toString(), "arg");
   }
 
   void slf4j() {
-    LOG.debug("str " + toString());
-    LOG.debug((Marker) null, "str " + toString());
+    LOG.debug("str {}", toString());
+    LOG.debug((Marker) null, "str {}", toString());
 
     // Flagged but not auto-fixed.
     LOG.debug("{} " + toString(), "arg");
     LOG.debug((Marker) null, "{} " + toString(), "arg");
   }
 }

Identification

Shows code lines which will (not) be flagged by this bug pattern.
A //BUG: Diagnostic contains: comment is placed above any violating line.

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import static com.google.common.base.Verify.verify;
import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.SoftAssertions.assertSoftly;

import java.util.Formatter;
import java.util.Locale;
import org.assertj.core.api.Assertions;
import org.assertj.core.api.BDDAssertions;
import org.assertj.core.api.Fail;
import org.assertj.core.api.ThrowableAssertAlternative;
import org.assertj.core.api.WithAssertions;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.slf4j.Marker;

class A {
  private static final Logger LOG = LoggerFactory.getLogger(A.class);

  void negative() {
    hashCode();
    equals(new A());
    equals(toString());
    equals(0);
    equals("str");
    equals("str" + 0);
    equals(0 + 0);
    equals(0 - 0);
    equals("str " + toString());
  }

  void assertj() {
    assertThat(0).overridingErrorMessage(toString());
    assertThat(0).overridingErrorMessage("str");
    assertThat(0).overridingErrorMessage("str " + 0);
    assertThat(0).overridingErrorMessage("str %s", 2 * 3);
    assertThat(0).overridingErrorMessage("str %s", toString());
    // BUG: Diagnostic contains:
    assertThat(0).overridingErrorMessage("str " + hashCode() / 2);
    // BUG: Diagnostic contains:
    assertThat(0).overridingErrorMessage(("str " + toString()));
    // BUG: Diagnostic contains:
    assertThat(0).overridingErrorMessage("str " + toString());
    // BUG: Diagnostic contains:
    assertThat(0).overridingErrorMessage("%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    assertThat(0).withFailMessage("str " + toString());
    // BUG: Diagnostic contains:
    assertThat(0).withFailMessage("%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    assertSoftly(softly -> softly.fail("str " + toString()));
    // BUG: Diagnostic contains:
    assertSoftly(softly -> softly.fail("%s " + toString(), "arg"));
    assertSoftly(softly -> softly.fail("str " + toString(), new Throwable()));

    // BUG: Diagnostic contains:
    assertThat("").isEqualTo("str " + toString());
    // BUG: Diagnostic contains:
    assertThat("").isEqualTo("%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    assertThat(new Error()).hasMessage("str " + toString());
    // BUG: Diagnostic contains:
    assertThat(new Error()).hasMessage("%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    assertThat(new Error()).hasMessageContaining("str " + toString());
    // BUG: Diagnostic contains:
    assertThat(new Error()).hasMessageContaining("%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    assertThat(new Error()).hasMessageEndingWith("str " + toString());
    // BUG: Diagnostic contains:
    assertThat(new Error()).hasMessageEndingWith("%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    assertThat(new Error()).hasMessageStartingWith("str " + toString());
    // BUG: Diagnostic contains:
    assertThat(new Error()).hasMessageStartingWith("%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    assertThat(new Error()).hasRootCauseMessage("str " + toString());
    // BUG: Diagnostic contains:
    assertThat(new Error()).hasRootCauseMessage("%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    assertThat(new Error()).hasStackTraceContaining("str " + toString());
    // BUG: Diagnostic contains:
    assertThat(new Error()).hasStackTraceContaining("%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    assertThat(0).as("str " + toString());
    // BUG: Diagnostic contains:
    assertThat(0).as("%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    assertThat(0).describedAs("str " + toString());
    // BUG: Diagnostic contains:
    assertThat(0).describedAs("%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    ((ThrowableAssertAlternative) null).withMessage("str " + toString());
    // BUG: Diagnostic contains:
    ((ThrowableAssertAlternative) null).withMessage("%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    ((ThrowableAssertAlternative) null).withMessageContaining("str " + toString());
    // BUG: Diagnostic contains:
    ((ThrowableAssertAlternative) null).withMessageContaining("%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    ((ThrowableAssertAlternative) null).withMessageEndingWith("str " + toString());
    // BUG: Diagnostic contains:
    ((ThrowableAssertAlternative) null).withMessageEndingWith("%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    ((ThrowableAssertAlternative) null).withMessageStartingWith("str " + toString());
    // BUG: Diagnostic contains:
    ((ThrowableAssertAlternative) null).withMessageStartingWith("%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    ((ThrowableAssertAlternative) null).withStackTraceContaining("str " + toString());
    // BUG: Diagnostic contains:
    ((ThrowableAssertAlternative) null).withStackTraceContaining("%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    ((WithAssertions) null).fail("str " + toString());
    // BUG: Diagnostic contains:
    ((WithAssertions) null).fail("%s " + toString(), "arg");
    ((WithAssertions) null).fail("str " + toString(), new Throwable());

    // BUG: Diagnostic contains:
    Assertions.fail("str " + toString());
    // BUG: Diagnostic contains:
    Assertions.fail("%s " + toString(), "arg");
    Assertions.fail("str " + toString(), new Throwable());

    // BUG: Diagnostic contains:
    BDDAssertions.fail("str " + toString());
    // BUG: Diagnostic contains:
    BDDAssertions.fail("%s " + toString(), "arg");
    BDDAssertions.fail("str " + toString(), new Throwable());

    // BUG: Diagnostic contains:
    Fail.fail("str " + toString());
    // BUG: Diagnostic contains:
    Fail.fail("%s " + toString(), "arg");
    Fail.fail("str " + toString(), new Throwable());
  }

  void guava() {
    checkArgument(true);
    checkArgument(true, toString());
    checkArgument(true, "str");
    checkArgument(true, "str " + 0);
    checkArgument(true, "str %s", 2 * 3);
    checkArgument(true, "str %s", toString());
    // BUG: Diagnostic contains:
    checkArgument(true, "str " + hashCode() / 2);
    // BUG: Diagnostic contains:
    checkArgument(true, ("str " + toString()));
    // BUG: Diagnostic contains:
    checkArgument(true, "str " + toString());
    // BUG: Diagnostic contains:
    checkArgument(true, "%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    checkNotNull(true, "str " + toString());
    // BUG: Diagnostic contains:
    checkNotNull(true, "%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    checkState(true, "str " + toString());
    // BUG: Diagnostic contains:
    checkState(true, "%s " + toString(), "arg");

    // BUG: Diagnostic contains:
    verify(true, "str " + toString());
    // BUG: Diagnostic contains:
    verify(true, "%s " + toString(), "arg");
  }

  void jdk() {
    String.format("str");
    String.format("str " + 0);
    String.format("str {}", 2 * 3);
    String.format("str {}", toString());
    // BUG: Diagnostic contains:
    String.format("str " + hashCode() / 2);
    // BUG: Diagnostic contains:
    String.format(("str " + toString()));
    // BUG: Diagnostic contains:
    String.format("str " + toString());
    // BUG: Diagnostic contains:
    String.format("{} " + toString(), "arg");

    String.format(Locale.ROOT, "str");
    String.format(Locale.ROOT, "str " + 0);
    String.format(Locale.ROOT, "str {}", 2 * 3);
    String.format(Locale.ROOT, "str {}", toString());
    // BUG: Diagnostic contains:
    String.format(Locale.ROOT, ("str " + toString()));
    // BUG: Diagnostic contains:
    String.format(Locale.ROOT, "str " + toString());
    // BUG: Diagnostic contains:
    String.format(Locale.ROOT, "{} " + toString(), "arg");

    // BUG: Diagnostic contains:
    new Formatter().format("str " + toString());
    // BUG: Diagnostic contains:
    new Formatter().format("{} " + toString(), "arg");

    // BUG: Diagnostic contains:
    new Formatter().format(Locale.ROOT, "str " + toString());
    // BUG: Diagnostic contains:
    new Formatter().format(Locale.ROOT, "{} " + toString(), "arg");
  }

  void slf4j() {
    LOG.debug("str");
    LOG.debug("str " + 0);
    LOG.debug("str {}", 2 * 3);
    LOG.debug("str {}", toString());
    // BUG: Diagnostic contains:
    LOG.debug("str " + hashCode() / 2);
    // BUG: Diagnostic contains:
    LOG.debug(("str " + toString()));
    // BUG: Diagnostic contains:
    LOG.debug("str " + toString());
    // BUG: Diagnostic contains:
    LOG.debug("{} " + toString(), "arg");

    LOG.debug((Marker) null, "str");
    LOG.debug((Marker) null, "str " + 0);
    LOG.debug((Marker) null, "str {}", 2 * 3);
    LOG.debug((Marker) null, "str {}", toString());
    // BUG: Diagnostic contains:
    LOG.debug((Marker) null, ("str " + toString()));
    // BUG: Diagnostic contains:
    LOG.debug((Marker) null, "str " + toString());
    // BUG: Diagnostic contains:
    LOG.debug((Marker) null, "{} " + toString(), "arg");

    // BUG: Diagnostic contains:
    LOG.error("str " + toString());
    // BUG: Diagnostic contains:
    LOG.error("{} " + toString(), "arg");

    // BUG: Diagnostic contains:
    LOG.error((Marker) null, "str " + toString());
    // BUG: Diagnostic contains:
    LOG.error((Marker) null, "{} " + toString(), "arg");

    // BUG: Diagnostic contains:
    LOG.info("str " + toString());
    // BUG: Diagnostic contains:
    LOG.info("{} " + toString(), "arg");

    // BUG: Diagnostic contains:
    LOG.info((Marker) null, "str " + toString());
    // BUG: Diagnostic contains:
    LOG.info((Marker) null, "{} " + toString(), "arg");

    // BUG: Diagnostic contains:
    LOG.trace("str " + toString());
    // BUG: Diagnostic contains:
    LOG.trace("{} " + toString(), "arg");

    // BUG: Diagnostic contains:
    LOG.trace((Marker) null, "str " + toString());
    // BUG: Diagnostic contains:
    LOG.trace((Marker) null, "{} " + toString(), "arg");

    // BUG: Diagnostic contains:
    LOG.warn("str " + toString());
    // BUG: Diagnostic contains:
    LOG.warn("{} " + toString(), "arg");

    // BUG: Diagnostic contains:
    LOG.warn((Marker) null, "str " + toString());
    // BUG: Diagnostic contains:
    LOG.warn((Marker) null, "{} " + toString(), "arg");
  }
}