Quick Assist

Quick assists perform local code transformations. They are invoked on a selection or a single cursor in the Java editor and use the same shortcut as quick fixes (Ctrl+1), but quick assist are usually hidden when an error is around. To show them even with errors present on the same line, press Ctrl+1 a second time.

A selection of quick assists can be assigned to a direct shortcut. By default, these are:

Assign more shortcuts or change the default shortcuts on the Opens keys preference page General > Keys preference page (in the 'Source' category).

A quick assist light bulb can be turned on on the Opens Java editor preference page Java > Editor preference page.

Name Code example Invocation location
Inverse if statement if (x) a(); else b(); > if (!x) b(); else a(); On 'if' statements with 'else' block
Convert to if-!-return if (x == 1) a(); > if (x != 1) return;
a(); 		On an 'if' statement
Inverse boolean expression a && !b > !a || b On a boolean expression
Invert local variable boolean a = false;
if (a) {} 		> boolean notA = true;
if (!notA) {} 		On a boolean variable
Invert equals a.equals(b) > b.equals(a) On a invocation of 'equals'
Inverse conditional expression x ? b : c > !x ? c : b On a conditional expression
Pull negation up b && c > !(!b || !c) On a boolean expression
Push negation down !(b && c) > !b || !c On a negated boolean expression
Remove extra parentheses if ((a == b) && (c != d)  {} > if (a == b && c != d)  {} On selected expressions
Put expression in parentheses return a > 10 ? 1 : 2; > return (a > 10) ? 1 : 2; On selected expression
Put expressions in parentheses if (a == b && c != d)  {} > if ((a == b) && (c != d))  {} On selected expressions
Join nested if statements if (a) { if (b) {} } > if (a && b) {} On a nested if statement
Swap nested if statements if (a) { if (b) {} } > if (b) { if (a) {} } On a nested if statement
Split if statement with and'ed expression if (a && b) {} > if (a) { if (b) {} } On an and'ed expression in a 'if'
Join selected 'if' statements with || if (a) x();  if (b) x(); > if (a || b) x(); On selected 'if' statements
Join 'if' sequence in if-else-if if (a) x();  if (b) y(); > if (a) x();  else if (b) y(); On selected 'if' statements
Split if statement with or'd expression if (a || b) x(); > if (a) x();  if (b) x(); On an or'd expression in a 'if'
If-else assignment to conditional expression if (a) x= 1; else x= 2; > x= a ? 1 : 2; On an 'if' statement
If-else return to conditional expression if (a) return 1;
else return 2; 		> return a ? 1 : 2; On an 'if' statement
Conditional expression assignment to If-else x= a ? 1 : 2; > if (a) x= 1; else x= 2; On a conditional expression
Conditional expression return to If-else return  a ? 1 : 2; > if (a) return 1; else return 2; On a conditional expression
Switch to If-else switch (kind) {
case 1: return -1;
case 2: return -2;
} 		> if (kind == 1) {
  return -1;
} else if (kind == 2) {
  return -2;
} 		On a switch statement
Convert if-else to switch if (kind == 1) {
  return -1;
} else if (kind == 2) {
  return -2;
} 		> switch (kind) {
case 1: return -1;
case 2: return -2;
} 		On an 'if' statement
Add missing case statements on enums switch (e){
} 		> switch (e){
case E1: break;
case E2: break;
} 		On a switch statement
Exchange operands a + b > b + a On an infix operation
Cast and assign if (obj instanceof Vector) {
} 		> if (obj instanceof Vector) {
 Vector vec= (Vector)obj;
} 		On an instanceof expression in an 'if' or 'while' statement
Use separate catch blocks try {
} catch (FileNotFoundException | InterruptedIOException e) {
} 		> try {
} catch (FileNotFoundException e) {
} catch (InterruptedIOException e) {
} 		On a multi-catch block (1.7 or higher)
Move exceptions to separate catch blocks try {
} catch (FileNotFoundException | InterruptedIOException | IllegalArgumentException e) {
} 		> try {
} catch (FileNotFoundException e) {
} catch (InterruptedIOException | IllegalArgumentException e) {
} 		On exceptions in a multi-catch clause (1.7 or higher)
Combine catch blocks try {
} catch (FileNotFoundException e) {
} catch (InterruptedIOException e) {
} 		> try {
} catch (FileNotFoundException | InterruptedIOException e) {
} 		On a catch block (1.7 or higher)
Add finally block try {
} catch (Exception e) {
} 		> try {
} catch (Exception e) {
} finally {} 		On a try/catch statement
Add else block if (a) b(); > if (a) b(); else { } On a if statement
Replace statement with block if (a) b(); > if (a) { b(); } On a if statement
Unwrap blocks { a() } > a() On blocks, if/while/for statements
Combine to single String String phrase= "one" + " two " + "three"; > String phrase= "one two three"; On a string concatenation expression
Pick out string "abcdefgh" > "abc" + "de" + "fgh" select a part of a string literal
Convert string concatenation to StringBuilder (J2SE 5.0) or StringBuffer "Hello " + name > StringBuilder builder= new StringBuilder();
builder.append("Hello ");
builder.append(name); 		select a string literal
Convert string concatenation to MessageFormat "Hello " + name > MessageFormat.format("Hello {0}", name); select a string literal
Split variable int i= 0; > int i; i= 0; On a variable with initialization
Join variable int i; i= 0; > int i= 0 On a variable without initialization
Assign to variable foo() > X x= foo(); On an expression statement
Extract to local foo(getColor()); > Color color= getColor();
foo(color); 		On an expression
Assign parameter to field public A(int color) {} > int fColor;
public A(int color) {
    fColor= color;
} 		On a parameter
Assign all parameters to new fields public A(int color, String name) {} > int fColor;
String fName;
public A(int color, String name) {
    fColor= color;
    fName= name;
} 		On a parameter
Array initializer to Array creation int[] i=  { 1, 2, 3 } > int[] i= new int[] { 1, 2, 3 } On an array initializer
Create 'for' loops void foo(Map<String, Integer> map) {
   map.keySet();
}
 		> void foo(Map<String, Integer> map) {
  for (String string : map.keySet()) {
  }
}
 		On arrays, Collections and Lists
Convert to 'enhanced for loop' (J2SE 5.0) for (Iterator i= c.iterator();i.hasNext();) {
}
 		> for (x : c) {
} 		On a for loop
Convert to indexed 'for' loop (J2SE 5.0) for (x : c) {
} 		> for (int i = 0; i < c.size(); i++) {
    x = c[i];
}
 		On an enhanced for loop
Convert to Iterator-based 'for' loop (J2SE 5.0) for (x : c) {
} 		> for (Iterator i= c.iterator();i.hasNext();) {
}
 		On an enhanced for loop
Create method in super class


On a method declaration
Rename in file


On identifiers
Rename in workspace


On identifiers
Extract to local variable a= b*8; > int x= b*8;
a= x; 		On expressions
Extract to constant a= 8; > final static int CONST= 8;
a= CONST; 		On expressions
Extract method int x= p * 5; > int x= getFoo(p); On expressions and statements
Inline local variable int a= 8, b= a; > int b= 8; On local variables
Convert local variable to field void foo() { int a= 8; } > int a= 8; void foo() {} On local variables
Convert anonymous to nested class new Runnable() { }; > class RunnableImplementation implements Runnable { } On anonymous classes
Convert to lambda expression Runnable r= new Runnable() {
  public void run() {}
}; 		> Runnable r= () -> {}; On anonymous classes implementing a functional interface (1.8 or higher)
Convert to anonymous class creation Runnable r= () -> {}; > Runnable r= new Runnable() {
  public void run() {}
}; 		On lambda expressions (1.8 or higher)
Convert to lambda expression Consumer<Integer> c= System.out::println; > Consumer<Integer> c= t -> System.out.println(t); On method references (1.8 or higher)
Convert to method reference Consumer<Integer> c= t -> System.out.println(t); > Consumer<Integer> c= System.out::println; On lambda expressions (1.8 or higher)
Change body expression to block Runnable r= () -> System.out.println(); > Runnable r= () -> {
  System.out.println();
}; 		On lambda expressions with body as expression (1.8 or higher)
Change body block to expression Runnable r= () -> {
  System.out.println();
}; 		> Runnable r= () -> System.out.println(); On lambda expressions with body as block (1.8 or higher)
Add inferred lambda parameter types Consumer<Integer> c= t -> System.out.println(t); > Consumer<Integer> c= (Integer t) -> System.out.println(t); On lambda expressions with inferred parameter types (1.8 or higher)
Add parentheses around lambda parameter Consumer<Integer> c= t -> System.out.println(t); > Consumer<Integer> c= (t) -> System.out.println(t); On lambda expressions (1.8 or higher)
Remove parentheses around lambda parameter Consumer<Integer> c= (t) -> System.out.println(t); > Consumer<Integer> c= t -> System.out.println(t); On lambda expressions (1.8 or higher)
Replace with getter and setter (Encapsulate Field) p.x; > p.getX(); On fields
Insert inferred type arguments List<String> list = new ArrayList<>(); > List<String> list = new ArrayList<String>(); On generic instance creation expressions (1.7 or higher)
Convert type to var String s= new String("Hello"); > var s= new String("Hello"); On variable declaration which has initializer (10 or higher)
Convert var to inferred type var s= new String("Hello"); > String s= new String("Hello"); On variable declaration with type var (10 or higher)
Add 'var' type to lambda parameters Finder finder = (s1,s2) -> s1.indexOf(s2); > Finder finder = (var s1,var s2) -> s1.indexOf(s2); On lambda parameters without type (10 or higher)
Replace lambda parameter types with 'var' Finder finder = (String s1,String s2) -> s1.indexOf(s2); > Finder finder = (var s1,var s2) -> s1.indexOf(s2); On lambda parameters with type (10 or higher)
Replace 'var' in lambda parameter types with inferred types Finder finder = (var s1,var s2) -> s1.indexOf(s2); > Finder finder = (String s1,String s2) -> s1.indexOf(s2); On lambda parameters with type var (10 or higher)
Remove lambda parameter types Finder finder = (String s1,String s2) -> s1.indexOf(s2); > Finder finder = (s1,s2) -> s1.indexOf(s2); On lambda parameters with type (1.8 or higher)
Split switch case labels return switch (day) {
case MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY -> "weekday";
case SATURDAY, SUNDAY -> "weekend";
}; 		> return switch (day) {
case MONDAY -> "weekday";
case TUESDAY -> "weekday";
case WEDNESDAY -> "weekday";
case THURSDAY -> "weekday";
case FRIDAY -> "weekday";
case SATURDAY, SUNDAY -> "weekend";
}; 		On Switch Case Labels (12 or higher)

The following quick assists are available in the Properties File Editor:

Related concepts

Java Editor
Quick Fix and Quick Assist

Related references

Quick Fix
JDT actions