/*
* Copyright 2000-2017 JetBrains s.r.o.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.siyeh.igtest.performance.string_concatenation_in_loops;
import java.util.*;
public class StringConcatenationInLoop
{
public StringConcatenationInLoop()
{
}
public String foo()
{
String foo = "";
for(int i = 0; i < 5; i++)
{
(foo) = ((foo) <warning descr="String concatenation '+' in loop">+</warning> (" ") + (i));
foo += "abc"; // only first concatenation in the loop is reported for given variable
}
for(int i = 0; i < 5; i++)
{
foo <warning descr="String concatenation '+=' in loop">+=</warning> foo + " " + i;
}
for(int i = 0; i < 5; i++)
{
baz( foo + " " + i);
}
for(int i = 0; i < 5; i++)
{
if(bar())
{
return baz(("foo" + "bar"));
}
}
for(int i = 0; i < 5; i++)
{
if(bar())
{
throw new Error("foo" + i);
}
}
String s = "";
for(int i = 0; i < 5; i++) {
if(i > 2) {
s += i;
{
System.out.println(s);
break;
}
}
}
for(int i = 0; i < 5; i++) {
if(i > 2) {
s += i;
{
System.out.println(s);
{
break;
}
}
}
}
for(int i = 0; i < 5; i++) {
if(i > 2) {
s += i;
{
{
System.out.println(i);
}
break;
}
}
}
for(int i = 0; i < 5; i++) {
if(i > 2) {
s <warning descr="String concatenation '+=' in loop">+=</warning> i;
{
System.out.println(i);
}
System.out.println(i);
}
}
for (int i = 0; i < 10; i++) {
if (i == 5) {
// concatenated only on single iteration
s += i;
}
System.out.println(i);
}
List<String> strings = new ArrayList<>();
for (int i = 0; i < 10; i++) {
s += i;
if (s.length() > 0) {
strings.add(s); // the whole string is used on every iteration anyways: it's useless to create a StringBuilder here
}
}
for (int i = 0; i < 10; i++) {
s <warning descr="String concatenation '+=' in loop">+=</warning> i;
if (i == 5 && s.length() > 0) {
strings.add(s); // the whole string is used, but only once: it's still reasonable to migrate to StringBuilder
}
}
for (int i = 0; i < 10; i++) {
s <warning descr="String concatenation '+=' in loop">+=</warning> i;
if (s.length() > 50) {
strings.add(s); // the whole string is used, but it's recreated after the usage: it's still reasonable to migrate to StringBuilder
s = "";
}
}
for (int i = 0; i < 10; i++) {
s = (s == "") + "...";
}
for (int i = 0; i < 10; i++) {
s = ("xyz" <warning descr="String concatenation '+' in loop">+</warning> (i <warning descr="String concatenation '+' in loop">+</warning> s)) <warning descr="String concatenation '+' in loop">+</warning> "...";
}
System.out.println(foo);
return foo;
}
void test(String s) {
for(int i=0; i<10; i++) {
if(s != null) {
if(s.equals("xyz")) {
s += "xyz";
}
break;
}
}
}
void test2(String s, int flag) {
for(int i=0; i<10; i++) {
if(flag == 0) {
s<warning descr="String concatenation '+=' in loop">+=</warning>"xyz";
continue; // continue doesn't matters: we're still iterating in loop
}
System.out.println("oops");
}
}
void test3(String s, int flag) {
for(int i=0; i<10; i++) {
for(int j=0; j<10; j++) {
if(flag == 0) {
s<warning descr="String concatenation '+=' in loop">+=</warning>"xyz";
break; // breaking inner loop only: still concatenation in loop
}
}
}
}
void test4(String s, int flag) {
for(int i=0; i<10; i++) {
s = "x";
for(int j=0; j<10; j++) {
if(flag == 0) {
s+="xyz";
break; // breaking inner loop only, but variable is always reassigned in outer loop, so effectively concatenating once
}
}
System.out.println(s);
}
}
void testLabel(String s, int flag) {
OUTER:
for(int i=0; i<10; i++) {
for(int j=0; j<10; j++) {
if(flag == 0) {
s+="xyz";
break OUTER; // breaking outer loop: ok
}
}
}
}
void testDefinedInLoop(List<?> list) {
for(Object obj : list) {
String s = "message";
if(obj != null) {
s+=obj; // replacing with StringBuilder won't change anything
}
System.out.println(s);
}
}
public void testSwitch(int flag) {
String s = "";
for(int i=0; i<10; i++) {
if(i > 5) {
if(s != null) {
switch(flag) {
case 0:
s += "xyz";
break; // break switch, then break loop: effectively single concatenation
case 1:
s <warning descr="String concatenation '+=' in loop">+=</warning> "abc"; // fall-through
case 2:
s <warning descr="String concatenation '+=' in loop">+=</warning> "efg"; // continue loop: possibly multiple concatenations
continue;
}
}
break;
}
}
System.out.println(s);
}
private boolean bar()
{
return true;
}
private String baz(String s)
{
return s;
}
public void oper() {
final String[] array = new String[] { "a", "a", "a" };
String s = "asdf";
final int len = array.length;
for (int k = 0; k < len; k++) {
array[k] += "b";
s <warning descr="String concatenation '+=' in loop">+=</warning> k;
}
}
void bla() {
while (true) {
System.out.println("a" + "b" + "c");
}
}
String field;
StringConcatenationInLoop parent;
void fieldTest() {
for(int i=0; i<10; i++) {
field = this.field <warning descr="String concatenation '+' in loop">+</warning> "x";
}
for(int i=0; i<10; i++) {
this.field = field <warning descr="String concatenation '+' in loop">+</warning> "x";
}
for(int i=0; i<10; i++) {
this.field = this.field <warning descr="String concatenation '+' in loop">+</warning> "x";
}
for(int i=0; i<10; i++) {
this.field = parent.field + "x";
}
for(int i=0; i<10; i++) {
parent.field = this.field + "x";
}
for(int i=0; i<10; i++) {
parent.field = this.parent.field <warning descr="String concatenation '+' in loop">+</warning> "x";
}
}
}