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成员变量的默认值

成员变量的默认值

作者: mrjunwang | 来源:发表于2018-07-13 12:43 被阅读0次

    成员变量的默认值如下表:

    类型 默认值
    boolean False
    byte 0
    short 0
    int 0
    long 0L
    char \u0000
    float 0.0f
    double 0.0d
    object reference null

    可以编写一个测试的类来验证。

    package com.javacodegeeks.advanced.construction;
    
    public class InitializationWithDefaults {
        private boolean booleanMember;
        private byte byteMember;
        private short shortMember;
        private int intMember;
        private long longMember;
        private char charMember;
        private float floatMember;
        private double doubleMember;
        private Object referenceMember;
    
        public InitializationWithDefaults() {
            System.out.println( "booleanMember = " + booleanMember );
            System.out.println( "byteMember = " + byteMember );
            System.out.println( "shortMember = " + shortMember );
            System.out.println( "intMember = " + intMember );
            System.out.println( "longMember = " + longMember );
            System.out.println( "charMember = " +
                Character.codePointAt( new char[] { charMember }, 0  ) );
            System.out.println( "floatMember = " + floatMember );
            System.out.println( "doubleMember = " + doubleMember );
            System.out.println( "referenceMember = " + referenceMember );
        }
    
        public static main(String[] args) {
          final InitializationWithDefaults initializationWithDefaults = new InitializationWithDefaults();
        }
    }
    

    执行结果为

    booleanMember = false
    byteMember = 0
    shortMember = 0
    intMember = 0
    longMember = 0
    charMember = 0
    floatMember = 0.0
    doubleMember = 0.0
    referenceMember = null
    

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