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Java Tutorial : Java initializing fields

InitializeTest.java

public class InitializeTest
{
    // initialize to 10
    public int capacity = 10;

    // initialize to false
    private boolean flag = false;

    public InitializeTest()
    {

    }

    public static void main(String args[])
    {

        InitializeTest initializeTest = new InitializeTest();
        System.out.println("capacity : " + initializeTest.capacity);
        System.out.println("flag     : " + initializeTest.flag);

    }
}

Output

capacity : 10
flag     : false

public class InitializeConstructorTest
{
    
    public int capacity;

    private boolean flag;

    /*
     * Instance variables can be initialized in constructors, where error
     * handling or other logic can be used
     */
    public InitializeConstructorTest(int capacity, boolean flag)
    {
        if(capacity > 200)
        {
            this.capacity = capacity;
        }
        else
        {
            this.capacity = 0;
        }
        this.flag = flag;
    }

    public static void main(String args[])
    {

        InitializeConstructorTest initializeConstructorTest = new InitializeConstructorTest(100, true);
        System.out.println("capacity : " + initializeConstructorTest.capacity);
        System.out.println("flag     : " + initializeConstructorTest.flag);
    }
}