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String???Java??????????????

1. new String("hello")?"hello"?????

?Java?????????????????????????????String s1 = new String("hello")?String s2 = "hello"???????????

1.1 ??????

• s1 = new String("hello")?

  • ??main()??????
  • ???????s1????new????????
  • new????????????????
  • ???????s1??????
  • "hello"???????String?????
  • Java???????????String Constant Pool?????"hello"??????
  • ???????????????????????"hello"??????????????String?????
  • s1?????????????????????

• s2 = "hello"?

  • "hello"??????????String?????
  • Java??????????????"hello"??????
  • ??????????????????????????????s2?
  • s2?????????????????"hello"?????????

1.2 ????

• s1 == s2?

  • ??????String????????
  • ??s1?s2?????????????????????????????????????
  • ???s1 == s2????false?

• s1.equals(s2)?

  • String????equals()??????????????????
  • "hello"?????????String????????
  • ???s1.equals(s2)????true?

1.3 ???????

• s1????????????????"hello"???????
• s2?????????????"hello"?????????
• ??????????????==?????false?

2. String???????????

?Java??????????????????????????????????????????

String s3 = "helloworld";String s1 = "hello";String s2 = "world";String temp = s1 + s2;String finalStr = s3 + "test";

2.1 temp = s1 + s2

• s1 + s2???????????String???
• ????????????????????????????????
• ????????s1?s2?????????
• ?????????????String?????
• temp??????????????

2.2 finalStr = s3 + "test"

• "test"??????????String?????
• Java??????????????"test"????
• ???????????????????????
• s3 + "test"???????????String???
• ??String??????????s3?"test"?????????
• finalStr??????????????

2.3 ????

• temp == s1 + s2?

  • temp?????????s1 + s2????????
  • ???temp == s1 + s2????true?

• **finalStr == "helloworld" + "test"`?

  • "helloworld" + "test"???????????String???
  • ??String??????????"helloworldtest"???????
  • finalStr?????????"helloworldtest"???????????
  • ???finalStr == "helloworld" + "test"????true?

• temp.equals(s1 + s2)?

  • temp???????s1 + s2?????????
  • ???temp.equals(s1 + s2)????true?

• finalStr.equals("hello" + "world")?

  • "hello" + "world"?????????????finalStr?????????
  • ???finalStr.equals("hello" + "world")????true?

3. ??

• **String s = new String("hello")**???2????

  • 1??????????????"hello"???????
  • 0??????????????????"hello"??????

• **String s = "hello"**????1????

  • ??????????????"hello"??????

• ????????

  • ??????????????????????
  • ???????????????????????????????

• ???new??????????????????????????????????

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